Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3240854 A
Publication typeGrant
Publication dateMar 15, 1966
Filing dateSep 8, 1961
Priority dateSep 8, 1961
Publication numberUS 3240854 A, US 3240854A, US-A-3240854, US3240854 A, US3240854A
InventorsEwers Ronald Wilfred
Original AssigneeLaubman & Pank Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Manufacture of mouldable plastic articles
US 3240854 A
Images(1)
Previous page
Next page
Description  (OCR text may contain errors)

Mamh 1966 I R. w. EWER 3,240,854

MANUFACTURE OF MOULDABLE PLASTIC ARTICLES Filed Sept. 8, 1961 III STAGE A STAGE B STAGE E sun 1: 42

STAGE 6 United States Patent 3,240,854 MANUFACTURE OF MOULDABLE PLASTIC ARTICLES Ronald Wilfred Ewers, Torrens Park, South Australia,

Australia, assignor to Laubman & Pank Limited, Adelaide, South Australia, Australia Filed Sept. 8, 1961, Ser. No. 136,881 4 Claims. '(Cl. 264-236) This invention relates to improvements in the manufacture of mouldable plastic articles, for example in the manufacture of ophthalmic lenses cast from transparent plastic.

Plastic, such as allyl diglycol carbonate with benzoyl peroxide or isopropyl percarbonate as a catalyst, has been proposed for use in the manufacture of lenses. This resin when confined between polished glass surfaces and cured, results in an ophthalmic lens of high optical quality.

During the polymerization of this resin (allyl diglycol carbonate), considerable shrinkage takes place which necessitates use of resilient means associated with the casting dies. This resilient means has formerly consisted of a resilient spacer which is set between the dies, and in being so positioned, also functions as a spacer to give the desired thickness. In the past this problem has been overcome to a limited extent by making use of 0 rings between the polished dies. The O ring provided the necessary resilience when the catalyst resin was cured, and its thickness determined the lens thickness.

However, a number of problems have become evident with 0 rings:

In the first place, 0 rings of varying thickness are required due to the range of powers encountered in prescription work. Secondly, prism control is difficult to achieve because the O ring would require compression by different amounts around its periphery. Thirdly, with ophthalmic lenses the prescription normally requires a toroidal surface on one side of the lens combination with a spherical surface on the other. This requirement plus variations in the specification of center thickness to cover the range of powers mentioned above would call for the use of over five hundred different gaskets to cover the range of lenses required for perscription work.

With the object of overcoming the abovementioned problems and simplifying the production of lenses, the method according to this invention comprises the steps of inserting a pair of complementary dies into an enveloping tube of deformable material, separating the dies, inserting a hollow injection conduit into the space between the dies, injecting catalyzed resin into said space, and at least partly curing the catalyzed resin while in said space.

For the invention to be more clearly understood, it is described in further detail with reference to an embodiment which is illustrated in the accompanying drawings, in which:

FIG. 1 shows diagrammatically steps in the method according to the invention,

According to the embodiment of the invention disclosed in the drawing a pair of dies and 11 formed from suitable glass with ground and polished surfaces of the desired contour are carefully washed with acetone, then with detergent and water and finally with water, and are then dried with a soft cloth. The dies 10 and 11 are then inserted with interference fit into a short length of tubing 12 of vinyl plastic (stage B).

After inserting one of the dies into the tubing 12, it is further cleaned with compressed air, and the complementary die is also similarly cleaned, so as to remove any trace of dust. The tubing being an interference fit over the dies 10 and 11 retains the dies in the position in which they are placed. The assembly of the complementary dies 10 and 11 within the tubing 12 is then placed in a die positioning means 13 (stage C).

The steps of the method of casting an optical lens are as follows:

After the assembly of dies 10 and 11 in the vinyl tubing 12 has been placed in the die positioning means 13, the vinyl tube 12 is lifted at the locality of one of the dies and air at pressure is introduced between the dies 10 and 11 by means of the air compressor hose 38, and the dies 10 and 11 are then moved outwardly under air pressure against the bull-nosed pins 33 and the ball points 24 respectively (stage D). The slidable V blocks '31 are then moved in by finger pressure to engage and retain the assembly of dies 10 and 11 in the tubing 12. Alternatively, the dies are clamped in the. V blocks first. A hollow injection conduit 40, which in this embodiment is a hyodermic syringe, is then inserted between the die 11 and'the tubing 12, and catalyzed resin is injected into the space between the dies 10 and 11. The air within the cavity escapes between the wall of the die 11 and the plastic tubing 12 where the tubing is spread away from the wall of the die to allow entry of the needle. This is illustrated in FIG. 1 as stage E, and the assembly is then transferred to an oven 42 (stage F) where the plastic resin between the dies is cured.

The catalyst concentration used in this embodiment is from two to five percent of benzoyl peroxide (or isopropyl percarbonate) in allyl diglycol carbonate. With benzoyl peroxide as the catalyst the initial curing cycle is approximately twelve hours with a starting temperature of 65 degrees C. slowly rising to degrees C. during this period. With isopropyl percarbonate as the catalyst the cycle would be approximately sixteen hours and the temperature 40 degrees C. to 80 degrees C. These times and temperatures vary according to the thickness of the lenses and oven efiiciency.

The oven efliciency is of importance since the curing is exothermic and the oven must handle the dissipated heat. Thus air circulation within the oven and general sensitivity of the oven are factors in the determination of permissible rate of heat increase.

During this heating cycle the plastic tubing 12 becomes soft and readily follows the contour of the edge of the plastic lens and allows inward movement of the dies as shrinkage takes place. At the completion of the curing cycle the dies are removed from the vinyl envelope and separated from the plastic lens and then re-assembled using a soft tissue 44 as a spacer between the plastic lens and the dies so as to avoid readhesion during a post curing period (stage G) in an oven 45. This post curing is necessary to remove strain and to fully cure the resin, and is achieved by heating from ambient to degrees C. over a period of three hours and maintaining at 115 degrees C. for a further two hours.

While the plastic envelope can be used a number of times, it is essentially regarded as a disposable item because of its low cost.

It will be seen that many variations could be introduced. For example it is not considered essential that the cast plastic should be allyl diglycol carbonate but other plastics could be used making use of the process.

What I claim is:

1. A methodof manufacture of mouldable plastic atticles, said method comprising inserting a pair of complementary dies into an enveloping tube of deformable material with an interference fit, injecting a fluid under pressure between said dies to displace the dies to adjustable preestablished spaced and angular oriented limit positions within the tube while the dies are retained by and within the tube, injecting catalyzed resin into the space between the dies while allowing the fluid between the dies to Patented Mar. 15, 1966 3 escape and at least partially curing the catalyzed resin in situ in said space, during which time the tube softens and allows inward movement of the dies due to shrinkage.

2. A method as claimed in claim 1, wherein the thus partially cured resin is separated from the tube and dies and thereafter reinserted between the dies with separating spacer elements therebetween, after which the resin is completely cured.

3. A method as claimed in claim 1, wherein the dies are first Washed in acetone and then in water and thereafter cleaned with compressed air prior to insertion into the tube.

4. A method of manufacture of mouldable plastic articles comprising the steps of inserting a pair of complementary dies into an enveloping tube of constant crosssection deformable material, introducing air at pressure into the space between the dies to separate them while retained by and within the eveloping tube and urge the outer faces of the dies against pre-positioned locating means, inserting a hollow injection conduit into the space between the dies, injecting catalyzed resin into said space,

References Cited by the Examiner UNITED STATES PATENTS 806,783 12/1905 Dayton 18-26 2,298,429 10/ 1942 Smith 264-1 2,328,525 8/1943 Egolf 18-58 2,406,361 8/1946 Fairbank et a1. 264-1 2,542,386 2/1951 Beattie 1858 2,745,138 5/1956 Beattie 1826 3,038,210 6/1962 Hungerford et al. 18-58 FOREIGN PATENTS 1,018,486 1/1953 France.

ROBERT F. WHITE, Primary Examiner.

20 WILLIAM J. STEPHENSON, ALEXANDER H. BROD- MERKEL, Examiners.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US806783 *Dec 16, 1904Dec 12, 1905Ansel Jacob DaytonMold.
US2298429 *Aug 23, 1940Oct 13, 1942Univis Lens CompanyMethod and apparatus for automatic pressure control in molding of synthetic resinousmaterials
US2328525 *Aug 23, 1941Aug 31, 1943Rohm & HaasMethod of preparing sheets
US2406361 *Oct 16, 1942Aug 27, 1946Polaroid CorpMold for use in the manufacture of optical elements
US2542386 *Dec 3, 1947Feb 20, 1951John O BeattieManufacture of plastic lenses from monomeric materials
US2745138 *May 26, 1953May 15, 1956Optical Plastics CorpApparatus for the manufacture of plastic lenses from monomeric materials
US3038210 *Jun 6, 1955Jun 12, 1962Parmelee Plastics CoMethod of producing plastic lenses
FR1018486A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4091057 *Sep 1, 1976May 23, 1978Weber Hermann PCompression, thermoplastic resins
US4191717 *Jan 19, 1978Mar 4, 1980Weber Hermann PCasting process for plastic lenses
US4212836 *Sep 5, 1978Jul 15, 1980Corning Glass WorksHot pressing on low melting alloy casting
US4364878 *Feb 22, 1980Dec 21, 1982Omnitech Inc.Method for molding ophthalmic lenses
US4497754 *Mar 5, 1981Feb 5, 1985Societa' Italiana Lenti S.I.L.-S.R.L.Molding, heat treatment
US4540534 *Oct 11, 1983Sep 10, 1985American Optical CorporationPrevention of knit libe
US4693446 *Sep 20, 1985Sep 15, 1987Techna Vision, Inc.Gasket for molding plastic lenses
US5062254 *May 19, 1989Nov 5, 1991Raychem CorporationMethod for making an optical fiber coating dispenser package
US5407627 *Aug 3, 1992Apr 18, 1995Polycryl Enterprises Inc.Process and apparatus for forming stress-free thermosetting resin products
US5611969 *Mar 9, 1995Mar 18, 1997Essilor International, Compagnie Generale D'optiqueOptical lens mold and method of making the mold
US6419873Mar 19, 1999Jul 16, 2002Q2100, Inc.Photopolymerization
US6464484Mar 30, 2002Oct 15, 2002Q2100, Inc.Apparatus and system for the production of plastic lenses
US6528955Mar 30, 2000Mar 4, 2003Q2100, Inc.Ballast system for a fluorescent lamp
US6557734Feb 9, 2001May 6, 2003Q2100, Inc.Plastic lens systems, compositions, and methods
US6612828Feb 20, 2001Sep 2, 2003Q2100, Inc.Fill system with controller for monitoring use
US6632535Jun 8, 2000Oct 14, 2003Q2100, Inc.Method of forming antireflective coatings
US6634879Feb 9, 2001Oct 21, 2003Q2100, Inc.Plastic lens systems, compositions, and methods
US6655946Feb 20, 2001Dec 2, 2003Q2100, Inc.Apparatus for preparing an eyeglass lens having a controller for conveyor and curing units
US6676398Feb 20, 2001Jan 13, 2004Q2100, Inc.Apparatus for preparing an eyeglass lens having a prescription reader
US6676399Feb 20, 2001Jan 13, 2004Q2100, Inc.Apparatus for preparing an eyeglass lens having sensors for tracking mold assemblies
US6698708Mar 30, 2000Mar 2, 2004Q2100, Inc.Gasket and mold assembly for producing plastic lenses
US6702564Feb 20, 2001Mar 9, 2004Q2100, Inc.System for preparing an eyeglass lens using colored mold holders
US6709257Feb 20, 2001Mar 23, 2004Q2100, Inc.Eyeglass lens forming apparatus with sensor
US6712331Feb 20, 2001Mar 30, 2004Q2100, Inc.Holder for mold assemblies with indicia
US6712596Sep 14, 1999Mar 30, 2004Q2100, Inc.System for producing ultraviolet blocking lenses
US6716375Mar 30, 2000Apr 6, 2004Q2100, Inc.Apparatus and method for heating a polymerizable composition
US6723260Mar 30, 2000Apr 20, 2004Q2100, Inc.Method for marking a plastic eyeglass lens using a mold assembly holder
US6726463Feb 20, 2001Apr 27, 2004Q2100, Inc.Apparatus for preparing an eyeglass lens having a dual computer system controller
US6729866Feb 9, 2001May 4, 2004Q2100, Inc.Plastic lens systems
US6752613Feb 20, 2001Jun 22, 2004Q2100, Inc.Apparatus for preparing an eyeglass lens having a controller for initiation of lens curing
US6758663Feb 20, 2001Jul 6, 2004Q2100, Inc.System for preparing eyeglass lenses with a high volume curing unit
US6790022Feb 20, 2001Sep 14, 2004Q2100, Inc.Apparatus for preparing an eyeglass lens having a movable lamp mount
US6790024Feb 20, 2001Sep 14, 2004Q2100, Inc.Apparatus for preparing an eyeglass lens having multiple conveyor systems
US6808381Feb 20, 2001Oct 26, 2004Q2100, Inc.Apparatus for preparing an eyeglass lens having a controller
US6840752Feb 20, 2001Jan 11, 2005Q2100, Inc.Apparatus for preparing multiple eyeglass lenses
US6863518Feb 20, 2001Mar 8, 2005Q2100, Inc.Mold filing apparatus having multiple fill stations
US6875005Feb 20, 2001Apr 5, 2005Q1200, Inc.Apparatus for preparing an eyeglass lens having a gating device
US6893245Feb 20, 2001May 17, 2005Q2100, Inc.Apparatus for preparing an eyeglass lens having a computer system controller
US6899831Feb 20, 2001May 31, 2005Q2100, Inc.Method of preparing an eyeglass lens by delayed entry of mold assemblies into a curing apparatus
US6926510Jul 3, 2002Aug 9, 2005Q2100, Inc.Plastic lens systems and compositions
US6939899Dec 23, 2002Sep 6, 2005Q2100, Inc.Eyeglass lens forming composition containing light absorbing compounds which may undergo light initiated polymerization
US6960312Oct 15, 2002Nov 1, 2005Q2100, Inc.Methods for the production of plastic lenses
US6962669Feb 20, 2001Nov 8, 2005Q2100, Inc.Computerized controller for an eyeglass lens curing apparatus
US6964479Aug 15, 2002Nov 15, 2005Q1200, Inc.Plastic lens system, compositions, and methods
US7004740Feb 20, 2001Feb 28, 2006Q2100, Inc.Apparatus for preparing an eyeglass lens having a heating system
US7011773Feb 20, 2001Mar 14, 2006Q2100, Inc.Graphical interface to display mold assembly position in a lens forming apparatus
US7025910Feb 20, 2001Apr 11, 2006Q2100, IncMethod of entering prescription information
US7037449Feb 20, 2001May 2, 2006Q2100, Inc.Method for automatically shutting down a lens forming apparatus
US7044429Mar 15, 2002May 16, 2006Q2100, Inc.Methods and systems for coating eyeglass lens molds
US7045081Feb 20, 2001May 16, 2006Q2100, Inc.Method of monitoring components of a lens forming apparatus
US7051290Feb 20, 2001May 23, 2006Q2100, Inc.Useful for curing multiple eyeglass lenses in a continuous manner using activating light
US7052262Feb 20, 2001May 30, 2006Q2100, Inc.System for preparing eyeglasses lens with filling station
US7060208Feb 20, 2001Jun 13, 2006Q2100, Inc.Method of preparing an eyeglass lens with a controller
US7074352Feb 20, 2001Jul 11, 2006Q2100, Inc.Graphical interface for monitoring usage of components of a lens forming apparatus
US7079920Feb 9, 2001Jul 18, 2006Q2100, Inc.Plastic lens systems, compositions, and methods
US7083404Feb 20, 2001Aug 1, 2006Q2100, Inc.System for preparing an eyeglass lens using a mold holder
US7124995Feb 20, 2001Oct 24, 2006Q2100, Inc.Holder for mold assemblies and molds
US7139636Feb 20, 2001Nov 21, 2006Q2100, Inc.System for preparing eyeglass lenses with bar code reader
WO2001074572A2 *Mar 30, 2001Oct 11, 2001Q2100 IncApparatus and method for heating a polymerizable composition
Classifications
U.S. Classification264/236, 264/2.6, 264/313, 264/2.2, 264/39
International ClassificationB29D11/00, B29C33/00
Cooperative ClassificationB29C33/0038, B29D11/00413, B29D11/00432, B29D11/00538, B29L2031/7602, B29D11/00528
European ClassificationB29D11/00C25E, B29D11/00C25F, B29D11/00C20, B29C33/00E, B29D11/00C22